In-situ detoxification method for heavily contaminated site by hexavalent chromium, chromium soil remediation microbial agent and preparation method thereof

Abstract

Disclosed is an in-situ detoxification method for a heavily contaminated site by hexavalent chromium. The method includes injecting a chemical reducing agent into a site heavily contaminated with hexavalent chromium, and injecting a chromium soil remediation microbial agent into the site after 0-10 days. The in-situ detoxification method includes: first, in-situ injecting the chemical reducing agent into the soil, preliminarily reducing high-concentration hexavalent chromium such that the hexavalent chromium of high concentration has no toxic effect on the subsequent ecological microbial agent, then in-situ injecting the ecological microbial agent prepared from biogas residue, a carbon source and sulfate into the chromium-containing soil under pressure, and forming a large-scale reducing buffer zone containing sulfate-reducing bacteria and sulfide in a special maintenance manner in the subsurface soil of the site to reduce the hexavalent chromium continuously and effectively.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of International Patent Application No. PCT / CN2017 / 086385, filed on May 27, 2017, which claims the benefit of priority from Chinese Application No. 201610370225.5, filed on May 30, 2016. The entire contents of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference.TECHNICAL FIELD[0002]The present application relates to the field of soil remediation, and in particular to an in-situ detoxification method for a site heavily contaminated with hexavalent chromium, a chromium soil remediation microbial agent and a preparation method thereof.BACKGROUND OF THE PRESENT INVENTION[0003]Chromium (Cr) and its compounds are the basic raw materials commonly used in metallurgy, metal processing, electroplating, tanning, paint, pigments and other industries. In the production process of the above-mentioned industries, a large amount of chromium-containing waste...

AI Technical Summary

Benefits of technology

[0037]1. The sulfate-reducing flora cultivated in this application is an indigenous flora, which has strong natural tolerance, is easy to multiply on a large scale in the site, and can permanently and efficiently reduce the hexavalent chromium without causing ecological problems.

[0038]2. The sulfate-reducing bacteria in the chromium soil remediation microbial agent reduces the sulfate of ferrous sulfate to form a sulfide, which avoids secondary contamination of the sulfate while more effectively reducing hexavalent chromium.

Problems solved by technology

In the production process of the above-mentioned industries, a large amount of chromium-containing waste gas, waste water and waste residue are generated, which causes serious environmental contamination problems.

Since Cr(VI) is a heavy metal that is soluble in water, and the site contaminated by Cr(VI) can be as deep as 100 meters sometimes, and how to remediate such chromium-containing soil which is heavily contaminated has always been a problem in the environmental protection field.

Although there are many treatment methods, most of them have various problems.

However, ferrous sulfate is low in pH, corrosive, and is easily oxidized and deactivated in the air.

Moreover, ferrous iron is easily adsorbed and intercepted by soil and has poor permeability.

In order to effectively treat chromium-containing soil, it is often necessary to add an excess of ferrous sulfate, which in turn tends to cause secondary pollution of sulfate radical.

Since ferrous iron is easily oxidized and deactivated in air, the method uses citric acid with a low pH to inhibit its oxidation and increase its permeation, but correspondingly increases the cost and acidifies the soil while still causing secondary pollution of sulfate.

However, this method may easily cause the microbial agent to be intercepted in a certain section of the soil through natural permeation, which causes the microbial agent to be unable to be transported, and the organic matter and the dissolved hexavalent chromium solution are permeated into the underground water, causing secondary contamination of the underground water.

In general, for the site contaminated with a high concentration of hexavalent chromium, traditional chemical reagents are difficult to reduce all the hexavalent chromium, and the microorganism reducing microbial agents are easily killed by high-concentration hexavalent chromium to be ineffective.